Myasthenia gravis is painless muscle
weakness that fatigues - in other words the muscles weaken more rapidly
on use than is normal. In addition, the symptoms typically worsen
towards the end of the day and after exercise. Myasthenia gravis affects
about one person in every 10,000 in the UK. The disorder can start at
any age from childhood onwards and the chance of developing it increases
with age. In the younger age group, women are affected about twice as
often as men are. However, in later life it is commoner in men than
women. The prognosis of myasthenia gravis is good. Using the array of
therapies that are now available, more than 90 percent of patients
return to near-normal function.

Between patients, the disease varies widely in severity and
pattern of progression. In the early stages, the weakness can be
intermittent. Often the first sign is drooping of the eyelids or double
vision. About 15 percent of patients only ever have eye muscle weakness
– this is called ocular myasthenia. The others also have more widespread
weakness - generalized myasthenia. These patients can develop weakness
of the face, swallowing, and chewing muscles, slurring of speech, and
weakness of the limbs and neck. In severe cases, weakness of the
breathing muscles can occur. Problems with swallowing or coughing can
cause choking. Chronic fatigue without weakness is not a feature of
myasthenia.